In accordance with the trend which is prevalent at the present time, many individuals are becoming increasingly aware of dietary restrictions. People are becoming concerned with their caloric intake and, in many instances, look favorably on foods which are low in calorie content. In addition to low calorie foods, people are also interested in beverages which fall within this category. This is readily apparent in the number of low calorie soft drinks which are presently on the market and which enjoy relatively large sales. Recently, within the past several years, alcoholic beverages which contain relatively few calories have become more popular. This trend toward beverages with low calorie content is exemplified by the switch of many beer drinkers to the so-called light beers. Inasmuch as a source of calories is found in the alcohol content of the beverage such as beer or wine, a necessity has arisen to produce a product which contains a relatively low alcohol content and yet retains flavor or taste which is acceptable in the public.
Many manufacturers of light beers have attempted to produce a beer which contains relatively few calories with a correspondingly low alcohol content and yet will retain the flavor or taste of a beer which will find favor with the general populace, said favorable taste characteristics including a sweet, malty taste which has a good clean end taste with no lingering or after-taste to spoil the experience. One method of accomplishing this purpose is to treat a beer with added water so that the alcohol content of the final product is within the desired limits. While the above discussion has been concentrated on beer as the alcoholic beverage, it is also contemplated that other beverages such as wine will also fall into this category and may be treated in a manner similar to that which is used in the treatment of beer.
However, by producing a product which contains a relatively low alcohol content, a problem has arisen in that the dilution with water of alcoholic beverages such as beer or wine has not won much favor due to problems in the taste of the alcoholic beverage, that being especially true in the beer industry. Likewise, the wine industry has a similar dilemma inasmuch as it is necessary to pick the grapes from which the wine is made at an earlier stage, thus obtaining grapes which contain less sugar content, and then having to interrupt the fermentation of the grapes to produce light wine. The industry has suffered by producing wines with great variations in taste. Another reason for producing alcoholic beverages with a low alcoholic content, but with palatable taste characteristics, is the accusation with which the industries have been faced concerning unnecessary intoxication of individuals with concurrent complications which arise therefrom such as traffic accidents.
Some prior U.S. patents have addressed the process for attaining alcohol-reduced beverages. For example, U.S. Pat. No. 3,291,613 discloses a process for manufacturing alcohol-reduced beverages in which an alcoholic beverage is heated under increased pressure following which the heated beverage is sprayed into a vacuum and collecting the droplets which result from said spraying to form a liquid. This liquid is then evaporated after being heated by utilizing the application of a vacuum. The steps of heating the liquid followed by vacuum-evaporating are repeated in a successive number in order to remove a portion of the alcoholic content of the beverage. Another U.S. Pat. No. 4,401,678 discloses a process for producing wine in which the grape juice which forms the wine for fermentation thereof is subjected to an ultrafiltration step which has the effect of removing alcohol as well as other components. However, the use of ultrafiltration is separate and distinct from the process of the present invention which utilizes a reverse osmosis system to obtain the desired result. For example, in ultrafiltration, the separation of components from each other is based on the size of the molecules of the components. The separation is effected by utilizing a porous membrane which possesses relatively large pores and thus is used to discriminate between the molecules of the various components based on the size of the molecules. In this respect, the membrane acts as a sieve, thus permitting molecules of relatively small size to pass through the membrane while rejecting the molecules which possess a larger size.
U.S. Pat. No. 3,552,574 discloses a reverse osmosis system which may be utilized to concentrate liquid foods by removing the water content and involves means in the unit for promoting turbulence whereby the surface of the membrane is scoured and thus prevents a concentration on the surface thereof.
U.S. Pat. No. 4,499,117 is directed to a method for the preparation of a low alcoholic content beverage by means of ultrafiltration. The patent utilizes a series of non-denaturing physical fractionation including ultrafiltration, reverse osmosis, and evaporating and distilling under vacuum, the ultimate product which is recovered being produced by the recovery and combination of the various retentates. However, the patent does not teach the net pressure range which is an integral part of the present invention nor does the patent speak to the fact that any portion of the retentate in the various steps should be recycled to the feed stream, but teaches in contrast to this, that the various fractions of the retentate step combined to form the final product.
In addition, British Patent Specification No. 1,447,505 relates to a process for the production of beer with a reduced, low or no alcohol content. This patent discloses a process for removing ethyl alcohol from beer using a membrane system which is operated in a batch-concentration type of system in which the beer which is being processed is either diluted with water prior to or subsequent to the process. However, this type of process possesses inherent disadvantages inasmuch as the concentrations of the other complex components which are present in the beer are altered, thereby leading to the probability that precipitates as well as other components which would foul the membrane can form. The precipitates and/or membrane foulants will therefore not only affect the taste of the beer, but will also reduce the productivity of the membrane system. In addition, the process which is described in this patent is operated at a relatively high pressure system, i.e., from 426 (3096 kPa) to 710 (5160 kPa) pounds per square inch (psi) while the inlet pressure is from about 28.4 (204.6 kPa) to 71 (511.5 kPa) psi. As will be shown in the following specification, it has now been discovered that the alcoholic content of a beverage may be reduced by utilizing a different reverse osmosis system in a continuous manner while employing a low net pressure of from about 50 (344.7 kPa) to about 250 (1723.7 kPa) psi and preferably at about 100 (689.5 kPa) psi. As another difference between this patent and the process of the present invention, the membrane which is utilized in the patent is permeable only to the alcohol and water constituents of the beer while in contrast, the membrane of the present invention is permeable to other constituents present in beer such as carbon dioxide, ethyl acetate, etc.
Other processes for obtaining a low alcohol content of beverages have involved a simultaneous dewatering and dealkylization of the beverages followed by reconstituting the beverage by the addition of water. However, this type of process is not acceptable in many instances. For example, in concentrating a beer to a level necessary to obtain a low alcohol product followed by the addition of water to reconstitute the beer, it has been found that when effecting the process at temperatures in the range of from about 2.degree. C. to about 5.degree. C., proteins which are present in the beer will precipitate out during the concentration. The addition of water will not resolubilize the proteins and thus permit the same to resume the former position in the beer. The loss of proteins by precipitation will, of course, constitute a disadvantage inasmuch as the precipitated proteins will be lost and thus lower the protein value of the beer. Furthermore, other disadvantages which may be present when utilizing such a process are that the taste of the low alcohol content beverage will not be the same as the taste present in the original beverage and thus, in many instances, constitute a detriment to the finished product.
As will hereinafter be shown in greater detail, a process has been developed in which low alcohol content beverages may be obtained utilizing a reverse osmosis process to reduce the alcohol content while permitting the desired alcohol content to be attained without any detrimental effects as to protein loss, change in taste, etc.